This invention relates to testing integrated circuits.
Integrated circuit manufacturing operations involve testing. Testing may be performed while integrated circuits are in wafer form or after individual die have been packaged. For example, tests may be performed on packaged die to investigate circuit performance under various environmental conditions.
In a typical test, trays of integrated circuits are loaded into a test handler. The trays may be, for example, trays that conform to Joint Electron Device Engineering Council (JEDEC) standards. The test hander contains a computer-controlled arm called a work press. The work press picks up the integrated circuits from the trays and presses them into electrical contact with an array of pins in a test fixture called a contactor for testing. The operation of pressing an integrated circuit into contact with the contactor is referred to as a touch down, because the integrated circuit touches the pins in the contactor.
The pins in the contactor are typically pogo pins that extend and retract to accommodate each new integrated circuit being tested. The process of using the pogo pins creates wear and debris. Unless the contactor is maintained properly, some of the pins may fail to provide adequate contact during a test.
Waiting for a contactor to fail during testing before performing maintenance is generally undesirable. Proper contactor maintenance therefore requires scheduling. In a typical scenario, test operators are asked to maintain log books in which they manually record how often each contactor is used during a test run. Serial numbers are printed on the sides of contactors for identification.
This type of manual record keeping process is prone to error. Operators often forget to make log book entries or make incorrect entries. Contactors are often transferred between different test environments, which imposes further burdens. If a contactor is transferred from one worksite to another, it may be difficult or impossible to properly transfer the log book and records that are associated with the contactor.
Proper maintenance of log book records is also complicated by the fact that it is sometimes necessary to abort a test run. When a run is aborted, the test handler is flushed. All integrated circuits in the handler during the flush process are run through the contactor, even though they are not tested. Because flushing the handler creates additional touch-down events but does not complete any tests, operators can become confused as to whether or not to record the touch-downs. Operators can also become confused when performing test preparation operations that involve running dummy units through the test handler, because contactor touch-down events take place without any related testing.
Because of these factors, it is difficult to maintain adequate usage records and contactors are sometimes not maintained properly. This can lead to corrupted test results and downtime on the test floor.
It would therefore be desirable to be able to provide improved techniques for gathering information on how often a given contactor is used.